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排序方式: 共有177条查询结果,搜索用时 34 毫秒
31.
32.
Sang-Bum Kim Young-Kook Kim Yun-Su Lim Myung-Soo Kim Hyun-Sik Hahm 《Korean Journal of Chemical Engineering》2003,20(6):1023-1025
A mechanistic study on the partial oxidation of methane to synthesis gas (H2 and CO) was conducted with supported nickel catalysts. To investigate the reaction mechanism, pulse experiments, O2-TPD, and a comparison of the moles of reactants and products were carried out. From the O2-TPD experiment, it was observed that the active catalyst in the synthesis gas production desorbed oxygen at a lower temperature.
In the pulse experiment, the temperature of the top of the catalyst bed increased with the pulses, whereas the temperature
of the bottom decreased. This suggests that there are two kinds of reactions, that is, the total oxidation of methane (exothermic)
at the top and reforming reactions (endothermic) at the bottom. From the comparison of the moles of reactants and products,
it was found that the moles of CO2, CH4 and H2O decreased as the moles of H2 and CO increased. The results support the mechanism that synthesis gas is produced through a two-step reaction mechanism:
the total oxidation of methane to CO2 and H2O takes place first, followed by the reforming reaction of the produced CO2 and H2O with residual CH4 to form synthesis gas.
This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University. 相似文献
33.
Hong-Soo Park Hyuk-Jae You Hye-Jin Jo II-Woo Shim Hyun-Sik Hahm Seong-Kil Kim Young-Geun Kim 《Journal of Coatings Technology and Research》2006,3(1):53-60
Three phosphorous functional groups were introduced in one structural unit of polymer backbone to enhance the flame retardancy
of PU coatings. In the first step, we synthesized tetramethylene bis(orthophosphate) (TBOP) that contained two phosphorus
functional groups in one structural unit. In the next step, we synthesized modified polyesters (ATBTP-10,-20,-30) that contained
triphosphorous groups by condensing polymerization of TBOP, 1,4-butanediol, trimethylolpropane, adipic acid, and phenylphosphonic
acid (PPA). The amount of PPA in the ATBTPs was 10, 20, and 30 wt%. Then, flame-retardant PU coatings (AHFC−10,−20,−30) were
prepared by curing ATBTPs with hexamethylene diisocyanate-biuret (curing agent) at room temperature. From the TGA analysis
of diphosphorus-modified polyester (ATBT) and ATBTPs, the residues of ATBT, ATBTP-10, ATBTP-20, and ATBTP-30 were 24.6, 27.5,
29.2, and 31.9%, respectively. From this result, it was found that the residue increased in relation to the amount of PPA.
Physical properties of the films of flame-retardant coatings were deteriorated with the addition of PPA (flame retarding component),
however, all the films of flame-retardant coatings, except AHFC-30, met the required physical properties standard for coatings.
Char lengths of the AHFCs measured by the 45° Meckel burner method were 2.9∼4.8 cm, and LOI values were 28∼31%, which indicates
that the prepared AHFCs showed good flame retardancy. 相似文献
34.
Sun-Hwa Yeon Dae-Hyun Shin Nam-Sun Nho Kyoung-Hee Shin Chang-Soo Jin Sung-Chan Nam 《Korean Journal of Chemical Engineering》2013,30(4):864-870
Effects of a Cu-based catalyst on the catalytic performance in alcohol-hydrocarbon synthesis from syngas have been investigated, using various supports. Under the different porosities of three supports (zinc oxide, activation carbon, and titanium dioxide), whereas Cu/ZnO produces one liquid phase of major mixed alcohols, Cu/AC and Cu/TiO2 create two phases, alcohol (~75%) and hydrocarbon (~25%). X-ray diffraction shows that CuO impregnated on supports undergoes a complete reduction of metallic copper Cu0, which is the real active phase in the catalytic process. The Cu/TiO2 catalyst showed the highest ethanol composition in a mixed alcohol phase under GHSV 18,000 h?1, 30 bar, and 300 °C. 相似文献
35.
36.
37.
Hyun-Jin Kim Tae-Yub Kwon Kyo-Han Kim Soon-Taek Kwon Dae-Hyun Cho Jun Sik Son 《Polymer Bulletin》2014,71(4):875-886
A functional dental adhesive resin system with antimicrobial properties was developed using human serum albumin (HSA) nanoparticles as the drug delivery carrier. HSA nanoparticles loaded with chlorhexidine (CHX) diacetate, a model antimicrobial drug, were prepared using a desolvation technique. The resulting CHX-loaded HSA nanoparticles were incorporated into a commercial methyl methacrylate (MMA)-based resin. The size of the nanoparticles ranged 50–300 nm, and the nanoparticles were dispersed homogeneously in the resin matrix. The CHX-loaded HSA nanoparticles showed an early release burst of ~20 % of the total CHX by day 5, followed by the sustained release of the remaining CHX over the next 20 days. In contrast, the resin matrix containing the HSA nanoparticles showed a sustained release of CHX without an early release burst in a 4-week immersion study. In the agar diffusion test, the resin matrix incorporating the CHX-loaded HAS nanoparticles showed a larger growth inhibition zone against Streptococcus mutans than the resin matrix alone, indicating that this delivery platform potently imparts antibacterial activity to the resins. These results also suggest that CHX, which inhibits the growth of oral bacteria, can be incorporated efficiently into the MMA-based resin matrix using HSA nanoparticles. 相似文献
38.
The crystallization of thin polymer film depends on surface/interface properties, due to the fact that molecular chain motion is affected by the presence of the surface. In this work, we measured the ferroelectric properties, crystallinity, chain conformation and surface morphologies of one-dimensionally confined P(VDF-TrFE) thin films using transfer-printed Au film, annealed at elevated temperatures, from just below melting temperature up to 200 °C. Crystallization at low temperature, i.e., below melting temperature, the confinement effect has been found to be negligible. At high temperatures, however, confined crystallization has led to superior ferroelectric properties, compared to samples annealed without confinement. These observations have led to two- or three-layer model for those crystallized thin films with or without confinement, respectively. Further, the transfer-printing of metal as a confining surface has been found to be beneficial, compared to vacuum evaporation, due to deposition-induced damages on organic polymer. This confinement-induced retention of ferroelectricity in P(VDF-TrFE) thin films above its melting temperature can extend processing temperature in organic devices using the ferroelectric polymer, such as non-volatile organic memory devices. 相似文献
39.
Nam Keun Lee In-Cheol Yeo Joung Whan Park Byung-Sun Kang Young Tae Hahm 《Journal of Bioscience and Bioengineering》2010,110(3):298-303
In this study, an effective substance was isolated from Bacillus subtilis SC-8, which was obtained from traditionally fermented soybean paste, cheonggukjang. The substance was purified by HPLC, and its properties were analyzed. It had an adequate antagonistic effect on Bacilluscereus, and its spectrum of activity was narrow. When tested on several gram-negative and gram-positive foodborne pathogenic bacteria such as Salmonella enterica, Salmonella enteritidis, Staphylococcus aureus, and Listeria monocytogenes, no antagonistic effect was observed. Applying the derivative from B. subtilis SC-8 within the same genus did not inhibit the growth of major soybean-fermenting bacteria such as Bacillus subtilis, Bacillus licheniformis, and Bacillus amyloquefaciens. The range of pH stability of the purified antagonistic substance was wide (from 4.0 to >10.0), and the substance was thermally stable up to 60 °C. In the various enzyme treatments, the antagonistic activity of the purified substance was reduced with proteinase K, protease, and lipase; its activity was partially destroyed with esterase. Spores of B. cereus did not grow at all in the presence of 5 μg/mL of the purified antagonistic substance. The isolated antagonistic substance was thought to be an antibiotic-like lipopeptidal compound and was tentatively named BSAP-254 because it absorbed to UV radiation at 254 nm. 相似文献
40.
Park OK Hahm MG Lee S Joh HI Na SI Vajtai R Lee JH Ku BC Ajayan PM 《Nano letters》2012,12(4):1789-1793
Highly conductive reduced graphene oxide (GO) polymer nanocomposites are synthesized by a well-organized in situ thermochemical synthesis technique. The surface functionalization of GO was carried out with aryl diazonium salt including 4-iodoaniline to form phenyl functionalized GO (I-Ph-GO). The thermochemically developed reduced GO (R-I-Ph-GO) has five times higher electrical conductivity (42,000 S/m) than typical reduced GO (R-GO). We also demonstrate a R-I-Ph-GO/polyimide (PI) composites having more than 10(4) times higher conductivity (~1 S/m) compared to a R-GO/PI composites. The electrical resistances of PI composites with R-I-Ph-GO were dramatically dropped under ~3% tensile strain. The R-I-Ph-GO/PI composites with electrically sensitive response caused by mechanical strain are expected to have broad implications for nanoelectromechanical systems. 相似文献